Loss investigations of high-frequency lithium niobate Lamb wave resonators at ultralow temperatures

Lamb wave resonators (LWRs) operating at ultralow temperatures serve as promising acoustic platforms for implementing microwave-optical transduction and radio frequency (RF) front-ends in aerospace communications because of the exceptional electromechanical coupling (k2) and frequency scalability. However, the properties of LWRs at cryogenic temperatures have not been well understood yet. Herein, we experimentally investigate the temperature dependence of the quality factor and resonant frequency in higher order antisymmetric LWRs down to millikelvin temperatures. High-frequency A1 and A3 mode resonators with spurious-free responses are comprehensively designed, fabricated, and characterized. The quality factors of A1 modes gradually increase upon cryogenic cooling, reaching values up to 4 times higher than those measured at room temperature, while A3 mode resonators exhibit a non-monotonic temperature dependence. Our findings provide insight into the loss mechanisms of cryogenic LWRs, paving the way for the development of strong-coupling quantum acoustodynamics and next-generation satellite wireless communication technologies.